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 * The Universal Permissive License (UPL), Version 1.0
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 * person obtaining a copy of this software, associated documentation and/or
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 * (a) the Software, and
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 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
 * portions of the Software.
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package com.oracle.truffle.api.bytecode;

import com.oracle.truffle.api.frame.FrameExtensions;
import com.oracle.truffle.api.memory.ByteArraySupport;

/**
 * Accessor class used to abstract away frame and bytecode array accesses in the generated code.
 *
 * Do not use directly.
 *
 * @since 24.2
 */
public abstract sealed class BytecodeDSLAccess permits BytecodeDSLCheckedAccess, BytecodeDSLUncheckedAccess {

    private static volatile BytecodeDSLAccess safeSingleton;
    private static volatile BytecodeDSLAccess unsafeSingleton;

    /**
     * Obtains an accessor. Used by generated code; do not use directly.
     *
     * @since 24.2
     */
    public static final BytecodeDSLAccess lookup(Object token, boolean allowUnsafe) {
        BytecodeRootNodes.checkToken(token);
        BytecodeDSLAccess impl;
        if (allowUnsafe && !Boolean.getBoolean("truffle.dsl.DisableUnsafeBytecodeDSLAccess")) {
            impl = unsafeSingleton;
            if (impl == null) {
                impl = unsafeSingleton = createUnsafe();
            }
        } else {
            impl = safeSingleton;
            if (impl == null) {
                impl = safeSingleton = createSafe();
            }
        }
        return impl;
    }

    BytecodeDSLAccess() {
    }

    private static BytecodeDSLAccess createSafe() {
        return new BytecodeDSLCheckedAccess();
    }

    private static BytecodeDSLAccess createUnsafe() {
        return new BytecodeDSLUncheckedAccess();
    }

    /**
     * Returns a {@link ByteArraySupport} to use for byte array accesses.
     *
     * @since 24.2
     */
    public abstract ByteArraySupport getByteArraySupport();

    /**
     * Returns a {@link FrameExtensions} to use for frame accesses.
     *
     * @since 24.2
     */
    public abstract FrameExtensions getFrameExtensions();

    /**
     * Reads from an int array.
     *
     * @since 24.2
     */
    public abstract int readInt(int[] arr, int index);

    /**
     * Writes to an int array.
     *
     * @since 24.2
     */
    public abstract void writeInt(int[] arr, int index, int value);

    /**
     * Reads from an Object array.
     *
     * @since 24.2
     */
    public abstract <T> T readObject(T[] arr, int index);

    /**
     * Writes to an Object array.
     *
     * @since 24.2
     */
    public abstract <T> void writeObject(T[] arr, int index, T value);

    /**
     * Casts a value to the given class. Also assumes non-null. If used in the form
     * uncheckedCast(this.field, ...) and the field is a final field, then the field will get
     * transformed into an immutable field read.
     *
     * @since 24.2
     */
    public abstract <T> T uncheckedCast(Object arr, Class<T> clazz);

}
